HI gpananos. Great questions. It is necessary to heat and then cool down the milk and maintain the temperature so that the cultures can grow. As for destroying properties of milk, I really don't know. Nutritionally, I love greek yogurt because it had higher protein levels than milk.

I agree. I was surprised too that it takes so long to reach 180 degrees F on medium low. I usually start heating on medium-low and then change to low when skin starts to form. This takes a bit longer. I checked another source and the time is similar. One of these days, I'm going to try the microwave. If you get different results, please let everyone know. Thanks for your comment.